Screws and other mechanical connecting parts are often surgically implanted in a patient to connect pieces of bone which are broken or weak due to injury or disease. A variety of occasions arise in which these screws and/or parts must later be removed. For example, screws may be surgically removed after the desired healing is achieved, or when the bone is not healing as expected, or in cases in which the screw was not oriented properly when first implanted by the surgeon. In still other cases, a screw implanted in a patient's spine may be pressing upon a nerve and causing the patient pain. The screw may thus need to be removed. Such screws, however, may have broken due to weakness in the screw as a result of repeated flexing and/or shock. In this instance, the broken screw pieces would thus need to be removed.
Various instruments for the removal of screws from bone have been known and described. A review of the art reveals that such instruments engage the head of the screw in order to remove the screw from the bone by an action applied by the instrument to the head of the screw. Typically, the screw head is engaged by a specially-designed tool which is used to rotate the screw or otherwise apply a force sufficient to retract the screw from the bone. The tool is designed to mate with the head of the screw. For example, in some cases, the screw head will have a corresponding socket formation to accommodate an Allen wrench or Phillips screw driver.
As noted, there are many occasions, however, in which a screw breaks, typically due to weakness from repeated flexing and/or shock. In that case, the remaining broken pieces of the screw cannot be removed with conventional tools which operate by driving engagement with the screw head, because the screw head has broken off. Thus, such tools, which are generally designed to mate with the screw head, cannot function and are completely ineffective if the screw head has broken off.
In addition, screw fragments can be lodged deep in bone and yet, it is desirable to remove as little bone as possible when removing the fragments.
There remains a need, therefore, for a device which can be used to remove a broken screw piece from the bone. There remains a need for such a device which does not require the head of the screw to be intact on the screw. There is a further need for a screw piece removal device which involves removal of as little bone as possible and which maintains the mechanical advantage of a comparatively long handle in that it has advantageous gripping action and is easily directed by a surgeon.